U.S. patent number 6,975,067 [Application Number 10/324,585] was granted by the patent office on 2005-12-13 for organic electroluminescent device and encapsulation method.
This patent grant is currently assigned to 3M Innovative Properties Company. Invention is credited to Fred B. McCormick, Jon E. Ottman, Raghunath Padiyath.
United States Patent |
6,975,067 |
McCormick , et al. |
December 13, 2005 |
Organic electroluminescent device and encapsulation method
Abstract
Organic electroluminescent devices and methods of preparing such
devices are provided. The organic electroluminescent devices
include a first electrode, a light emitting structure, a second
electrode, a conductive layer, and a non-conductive material. The
light emitting structure is disposed between the first and second
electrodes. The conductive layer is disposed on at least a portion
of the second electrode and is in electrical communication with the
second electrode through an opening in the non-conductive
material.
Inventors: |
McCormick; Fred B. (Maplewood,
MN), Ottman; Jon E. (Eagan, MN), Padiyath; Raghunath
(Woodbury, MN) |
Assignee: |
3M Innovative Properties
Company (St. Paul, MN)
|
Family
ID: |
32593491 |
Appl.
No.: |
10/324,585 |
Filed: |
December 19, 2002 |
Current U.S.
Class: |
313/512; 313/504;
313/506; 428/690 |
Current CPC
Class: |
H01L
51/5203 (20130101); H01L 51/5237 (20130101); H01L
51/5246 (20130101); H01L 51/5253 (20130101); H01L
51/5259 (20130101); H01L 27/3213 (20130101); H01L
27/3239 (20130101); H01L 27/3281 (20130101); H01L
2251/5338 (20130101); H01L 2251/5361 (20130101) |
Current International
Class: |
H05B 033/04 ();
H01L 051/20 () |
Field of
Search: |
;313/512,506,504,509,498,503,500 ;428/690 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 734 082 |
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Sep 1996 |
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EP |
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2000-195673 |
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Jul 2000 |
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JP |
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WO 98/55561 |
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Dec 1998 |
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WO |
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WO 99/40655 |
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Aug 1999 |
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WO |
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WO 00/18851 |
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Apr 2000 |
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WO |
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WO 00/26973 |
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May 2000 |
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WO |
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WO 00/36665 |
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Jun 2000 |
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WO |
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WO 00/70655 |
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Nov 2000 |
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WO |
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WO 01/81649 |
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Nov 2001 |
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WO |
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WO 02/05361 |
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Jan 2002 |
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WO |
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Other References
Friend et al.; "Electroluminescence in conjugated polymers" Nature;
vol. 397; Jan. 1999, pp. 121-128. .
Kraft et al.; "Electroluminescent Conjugated Polymers--Seeing
Polymers in a New Light"; Angew. Chem. Int. Ed. 1998 pp. 402-428.
.
Chen et al.; "Recent Developments in Molecular Organic
Electroluminescent Materials"; Macromol. Symp. 125 (1997) pp. 1-48.
.
Fujikawa et al.; "Energy structures of triphenylamine oligomers";
Synthetic Metals; 91 (1997) pp. 161-162. .
Grazulevicius et al.; "Charge-Transporting Polymers and Molecular
Glasses"; Handbook of Advanced Electronic and Photonic Materials
and Devices; vol. 10; 2001 pp. 233-274. .
"Hybrid Design For Organic Electroluminescent Devices", IBM
Technical Disclosure Bulletin, IBM Corp., New York, vol. 40, No. 9,
pp. 115-116, Sep. 1, 1997. .
Graff et al.; "Fabrication of OLED Devices on Engineered Plastic
Substrates"; 2000 Society of Vacuum Coaters ; 2000; pp. 397-400.
.
Mahon et al.; "Requirements of Flexible Substrates for Organic
Light Emitting Devices in Flat Panel Display Applications"; 1999
Society of Vacuum Coaters; 42nd Annual Technical Conference
Proceedings (1999) pp. 456-459. .
Affinito et al.; "A new method for fabricating transparent barrier
layers"; Thin Solid Films 290-291 (1996) pp. 63-67. .
Affinito et al. "PML/oxide/PML barrier layer performance
differences arising from use of UV or elctron beam polymerization
of the PML layers"; Thin Solid Films 308-309 (1997) pp. 19-25.
.
Affinito et al.; "Polymer-Oxide Transparent Barrier Layers"; 1996
Society of Vacuum Coaters; 39th Annual Technical Conference
Proceedings (1996) pp. 392-397..
|
Primary Examiner: Guharay; Karabi
Assistant Examiner: Roy; Sikkha
Attorney, Agent or Firm: Lown; Jean A.
Claims
We claim:
1. An organic electroluminescent device comprising: a) a first
electrode; b) a second electrode; c) a light emitting structure
disposed between the first and second electrodes; d) a conductive
layer disposed over at least a portion of the second electrode; and
e) a non-conductive material defining an opening through which the
conductive layer is in electrical communication with the second
electrode, said non-conductive material comprising a thermoplastic
polymeric material, wherein (i) the second electrode is in direct
contact with the non-conductive material in any portion of the
second electrode extending beyond the opening, (ii) the area of the
opening is smaller than the area of the surface of the second
electrode opposite the light emitting structure, and (iii) all
portions of a surface of the non-conductive layer opposite the
second electrode are in contact with the conductive layer.
2. The organic electroluminescent device of claim 1, wherein the
conductive layer extends beyond the periphery of the second
electrode and the non-conductive material separates the conductive
layer from the first electrode beyond the periphery of the second
electrode.
3. The organic electroluminescent device of claim 1, wherein the
thermoplastic polymeric material comprises an adhesive.
4. The organic electroluminescent device of claim 1, wherein the
device is encapsulated.
5. The organic electroluminescent device of claim 1, wherein the
first electrode comprises a transparent layer of a metal or metal
oxide.
6. The organic electroluminescent device of claim 1, wherein the
second electrode comprises an alkali metal, an alkaline earth
metal, n-doped silicon, or combination thereof.
7. The organic electroluminescent device of claim 1, wherein the
conductive layer comprises a deformable film.
8. The organic electroluminescent device of claim 1, wherein the
conductive layer comprises a metal.
9. The organic electroluminescent device of claim 1, further
comprising a substrate, wherein the substrate is substantially
transparent.
10. The organic electroluminescent device of claim 9, wherein the
substrate is flexible.
11. The organic electroluminescent device of claim 9, wherein the
substrate comprises a barrier construction.
12. The organic electroluminescent device of claim 11, wherein the
barrier construction comprises a metal oxide, metal nitride, metal
carbide, metal oxynitride or combination thereof.
13. The organic electroluminescent device of claim 9, wherein the
substrate, the conductive layer, or a combination thereof are
notched.
14. The organic electroluminescent device of claim 1, wherein the
device comprises a plurality of first electrodes and each first
electrode can be independently addressed.
15. The organic electroluminescent device of claim 1, wherein the
non-conductive material defines a plurality of openings and wherein
the conductive layer is in electrical communication with the second
electrode through the plurality of openings.
16. The organic electroluminescent device of claim 15, wherein the
plurality of openings are in a linear arrangement.
17. The organic electroluminescent device of claim 15, wherein the
device comprises a plurality of second electrodes and the plurality
of openings are aligned with the plurality of second
electrodes.
18. The organic electroluminescent device of claim 17, wherein the
device comprises a plurality of first electrodes aligned with the
plurality of second electrodes.
19. The organic electroluminescent device of claim 18, wherein each
pair of first and second electrodes can be independently
addressed.
20. The organic electroluminescent device of claim 1, wherein the
conductive layer extends beyond the periphery of the second
electrode, the non-conductive material separates the conductive
layer from the first electrode beyond the periphery of the second
electrode, and the first electrode extends beyond a periphery of
the conductive layer and the non-conductive material.
21. The organic electroluminescent device of claim 20, wherein the
first electrode is not patterned.
22. The organic electroluminescent device of claim 20, wherein the
second electrode is not patterned.
23. The organic electroluminescent device of claim 20, wherein the
first electrode faces a substrate and completely covers the
substrate.
24. The organic electroluminescent device of claim 1, wherein the
non-conductive material comprises a polymeric material and a
desiccant.
25. The organic electroluminescent device of claim 1, wherein the
opening in the non-conductive layer is positioned in an area of the
second electrode that is not directly above the light emitting
structure.
Description
FIELD OF THE INVENTION
The invention relates to organic electroluminescent devices and
methods of preparing organic electroluminescent devices. In
particular, organic electroluminescent devices are provided that
include a conducting layer such as a deformable foil in electrical
communication with one of the electrodes.
BACKGROUND OF THE INVENTION
Organic electroluminescent devices typically include an organic
electroluminescent material disposed between an anode and cathode.
The devices can contain electrode materials or electroluminescent
materials that are reactive with oxygen or moisture. Organic
electroluminescent devices that contain reactive materials are
usually encapsulated to extend the useful lifetimes of the devices.
Encapsulation methods typically involve positioning and sealing the
electrodes and electroluminescent material between two substrates
such as glass and polymeric materials or between a substrate and a
metal can. Various other protective layers can also be included to
further reduce contact of the reactive materials with oxygen and
water.
Organic electroluminescent devices are useful, for example, in a
variety of lighting applications and in the preparation of high and
low resolution displays.
SUMMARY OF THE INVENTION
Generally, the present invention relates to organic
electroluminescent devices and methods of preparing such
devices.
One aspect of the invention provides an organic electroluminescent
device that includes a first electrode, a second electrode, a light
emitting structure disposed between the first and second electrode,
a conductive layer disposed over at least a portion of the second
electrode, and a non-conductive material defining an opening
through which the conductive layer is in electrical communication
with the second electrode.
Another aspect of the invention provides a method of preparing an
organic electroluminescent device. An electroluminescent structure
is formed that includes a first electrode, a second electrode, and
a light emitting structure disposed between the first and second
electrodes. An opening is formed in a non-conductive material and
aligned with a surface of the second electrode. Electrical
communication is established between a conductive layer and the
second electrode through the opening in the non-conductive
material. The method can be a roll-to-roll process.
The above summary of the present invention is not intended to
describe each disclosed embodiment or every implementation of the
present invention. The Figures and the detailed description that
follow more particularly exemplify these embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention can be more completely understood in consideration of
the following detailed description of various embodiments of the
invention in connection with the accompanying drawings, in
which:
FIG. 1 is a schematic cross-sectional view of an organic
electroluminescent display construction.
FIG. 2 is a schematic cross-sectional view of a prior art organic
electroluminescent device.
FIG. 3 is a schematic cross-sectional view of one embodiment of an
organic electroluminescent device.
FIG. 4 is a schematic cross-sectional view of another embodiment of
an organic electroluminescent device.
FIG. 5 is a schematic cross-sectional view of yet another
embodiment of an organic electroluminescent device.
FIG. 6A is a schematic cross-sectional view of one embodiment of an
organic electroluminescent device having a substrate. FIG. 6B is a
schematic cross-sectional view of one embodiment of an organic
electroluminescent device having two substrates. FIG. 6C is a
schematic cross-sectional view of an organic electroluminescent
device having a substrate and edge seals. FIG. 6D is a schematic
cross-sectional view of an OEL device having a substrate and a
first electrode that extend beyond the outer periphery of the other
components of the device.
FIG. 7 is a schematic cross-sectional view of another embodiment of
an organic electroluminescent device having a substrate
FIG. 8 is a schematic cross-sectional view of yet another
embodiment of an organic electroluminescent device having a
substrate.
FIG. 9 is a schematic cross-sectional view of one embodiment of an
organic electroluminescent device having a substrate that includes
a barrier construction.
FIG. 10A is a schematic cross-sectional view of one embodiment of
an organic electroluminescent device having a plurality of second
electrodes. FIG. 10B is the corresponding schematic top view of
this embodiment.
FIG. 11A is a schematic cross-sectional view of one embodiment of
an organic electroluminescent device having a plurality of first
and second electrodes. FIG. 11B is a schematic cross-sectional view
of one embodiment of an organic electroluminescent device having a
plurality of first electrodes and single second electrode.
FIGS. 12A and 12B are schematic cross-sectional views of other
embodiments of organic electroluminescent devices having a
plurality of first and second electrodes. FIG. 12B includes a
non-conductive material between the pair of electrodes.
FIG. 13 is a schematic cross-sectional view of one embodiment of an
organic electroluminescent device having multiple openings in a
non-conductive material through which the conductive layer can be
in electrical communication with the second electrode.
FIG. 14a is a schematic cross-sectional view of one embodiment of
an organic electroluminescent device having V-shaped notches across
the substrate. FIG. 14b is a schematic cross-sectional view of one
embodiment of an organic electroluminescent device having V-shaped
notches across the conductive layer.
FIG. 15 is a schematic cross-sectional view of one embodiment of an
organic electroluminescent device in which the opening in the
non-conductive layer is in an area of the second electrode that is
not directly above the light emitting structure.
While the invention is amenable to various modifications and
alternative forms, specifics thereof have been shown by way of
example in the drawings and will be described in detail. It should
be understood, however, that the intention is not to limit the
invention to the particular embodiments described. On the contrary,
the intention is to cover all modifications, equivalents, and
alternatives falling within the spirit and scope of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
Organic electroluminescent devices and methods of preparing such
devices are provided. In particular, organic electroluminescent
devices are provided that include a conductive layer in electrical
communication with one of the electrodes through an opening in a
non-conductive material. Organic electroluminescent devices can be
used, for example, as backlights, low resolution displays, high
resolution displays, and the like.
As used herein, "organic electroluminescent device" or "OEL device"
refers to an article that includes a layer, or layers, of at least
one organic electroluminescent material disposed between a first
electrode and a second electrode. Typically, at least one of the
electrodes can transmit light emitted by the organic
electroluminescent material. As used herein, "organic
electroluminescent display" or "OEL display" refers to an article
that includes one or more organic electroluminescent devices.
R. H. Friend et al. in "Electroluminescence in Conjugated
Polymers," Nature, 397, p. 121 (1999), incorporated herein by
reference, describe one mechanism of the operation of organic
electroluminescent devices. Electrons are injected into the organic
electroluminescent material(s) from a cathode and holes are
injected into the organic electroluminescent material(s) from an
anode. As the injected charges migrate towards the oppositely
charged electrode, they can recombine to form electron-hole pairs
that are typically referred to as excitons. These excitons, or
excited state species, can emit energy in the form of light as they
decay back to a ground state. The region of the device in which the
excitons are generally formed can be referred to as the
recombination zone.
FIG. 1 shows a schematic cross-sectional view of one example of an
organic electroluminescent device or display 100. The structure
includes a device layer 110 and an optional substrate 120. Any
other suitable display component can also be included with the
device or display 100. Additional optional elements or devices 130
suitable for use with electronic displays or devices can be
provided between the OEL device or display 100 and viewer position
140.
The device layer 110 includes one or more OEL devices that emit
light through the optional substrate 120 toward a viewer position
140. The viewer position is used generically to indicate an
intended destination for the emitted light whether it be an actual
human observer, a screen, an optical component, an electronic
device, or the like.
Device layer 110 can include one or more OEL devices arranged in
any suitable manner. For example, in lamp applications (e.g.,
backlights for liquid crystal display (LCD) modules), device layer
110 can constitute a single OEL device that spans an entire
intended backlight area. Alternatively, in other lamp applications,
device layer 110 can constitute a plurality of closely spaced
devices that can be contemporaneously activated. For example,
relatively small and closely spaced red, green, and blue light
emitters can be patterned between common electrodes so that device
layer appears to emit white light when the emitters are activated.
Other arrangements for backlight applications are also
contemplated.
In some applications, the device layer 110 can include a plurality
of independently addressable OEL devices that emit the same or
different colors. Each device can represent a separate pixel or a
separate sub-pixel of a pixilated display (e.g., high resolution
display), a separate segment or sub-segment of a segmented display
(e.g., low information content display), or a separate icon,
portion of an icon, or lamp for an icon (e.g., indication
applications).
The optional element 130 can be any element or combination of
elements suitable for use with an OEL device or display 100. For
example, the optional element can include a liquid crystal display
module when device or display 100 is a backlight. One or more
polarizers or other elements, such as an absorbing or reflective
clean-up polarizer, can be provided between the liquid crystal
module and the backlight device or display 100. Alternatively, when
device or display 100 is an information display, optional element
130 can include one or more polarizers, wave plates, touch panels,
antireflective coatings, anti-smudge coatings, projection screens,
brightness enhancement films, or other optical components,
coatings, user interface devices, or the like.
FIG. 2 is a schematic cross-sectional view of a known organic
electroluminescent device 80. A first conductive layer is disposed
on a substrate 300. A portion of the conductive layer is removed or
patterned, for example, by etching to create an anode 20 and an
electrical contact 30. A light emitting structure 40 is disposed on
part of the surface of the anode 20 opposite the substrate 300. The
light emitting structure typically fills part of the patterned area
between the anode 20 and the electrical contact 30. A cathode 50 is
disposed on the light emitting structure 40 such that the light
emitting structure 40 is between the anode 20 and the cathode 50.
The cathode 50 extends into the patterned area and is in electrical
communication with the electrical contact 30. The light emitting
structure 40 and the cathode 50 are covered with a metal can 70 to
reduce exposure of these components of the device to oxygen and
moisture. The metal can 70 is insulated from the anode 20 and
electrical contact 30 by electrical insulating bodies 90. A gap 60
electrically insulates the metal can 70 from the second electrode
50.
As used herein, the term "pattern" means that a component (e.g.,
electrode or conductive layer) is divided into two or more
non-connected parts. In some embodiments, the component is
patterned by removal of part of the component. For example, the
component can be etched. In other embodiments, the component is
patterned by deposition of the component in two or more areas that
are not connected. For example, masks or printing methods can be
used to deposit the component. A "non-patterned" component refers
to a component that has not been divided into two or more
non-connected parts.
A device as shown in FIG. 2 is usually prepared using
photolithographic processes to pattern the first conductive layer
to form the anode 20 and electrical contact 30. Such processes
require the use of strong acids, for example, to etch the
conductive layer. Other manufacturing methods are desired.
The cathode and the light emitting structure are typically both
sensitive to degradation by moisture and oxygen. Encapsulation
methods are desirable that can extend the useful life of the
organic electroluminescent devices.
The organic electroluminescent devices of the present invention
include, but are not limited to, a first electrode, a second
electrode, a light emitting structure, a conductive layer, and a
non-conductive material. The light emitting structure is disposed
between the first and second electrode. The conductive layer can be
disposed on at least a portion of the second electrode and is in
electrical communication with the second electrode through at least
one opening defined in the non-conductive material.
As used herein, the term "non-conducting" or "non-conductive"
refers to a material that does not conduct electricity. Similarly,
as used herein, the term "conducting" or "conductive" refers to a
material that conducts electricity.
FIG. 3 is a schematic cross-sectional view of one embodiment of an
organic electroluminescent device 260 according to the invention. A
light emitting structure 220 is disposed between a first electrode
210 and a second electrode 230. The light emitting structure 220 is
in electrical communication with both electrodes 210 and 230. A
non-conductive layer 240 defines an opening 200. The opening 200 is
positioned in an area of a surface of the second electrode 230,
such as in an area of the surface that is opposite the light
emitting structure 220. A conductive layer 250 is typically in
electrical communication with the second electrode 230 through the
opening 200 defined by the non-conductive layer 240.
As shown in FIG. 3, the opening 200 in the non-conductive material
240 can be positioned entirely within an area of a surface of the
second electrode 230, such as the surface opposite the light
emitting structure 220. The area of the opening 200 is smaller than
the area of the surface of the second electrode 230 on which the
opening is positioned. The non-conductive material 240 can separate
the conductive layer 250 from the second electrode 230 near the
outer edges of the second electrode 230.
In some embodiments, the second electrode can extend beyond the
outer periphery of the light emitting structure. For example, in
FIG. 2 the second electrode (cathode 50) extends beyond the light
emitting structure 40. In such an embodiment, the opening in the
non-conductive layer can be positioned in an area of the second
electrode directly above the light emitting structure or positioned
in an area of the second electrode that is not directly above the
light emitting structure.
The conductive layer 250 in FIG. 3 can be bonded to the
non-conductive layer 240, both of which can extend beyond the outer
periphery of the second electrode 230. The non-conductive layer can
separate the conductive layer from other active components of the
device such as, for example, the light emitting structure, the
first electrode, or a combination thereof.
The non-conductive material 240 can be bonded to other components
of the OEL device. For example, in FIG. 3, the non-conductive
material 240 can be bonded to the first electrode 210 beyond the
outer periphery of the second electrode 230. Bonding one surface of
the non-conductive material can function as a seal and reduce
exposure of the light emitting material and the second electrode to
moisture or oxygen.
FIG. 15 is a schematic cross-sectional view of one embodiment of an
organic electroluminescent device 500 in which the opening 200 in
the non-conductive layer 240 is in an area of the second electrode
230 that is not directly above the light emitting structure
230.
The various components included in the organic electroluminescent
devices can provide encapsulation. As used herein, the term
"encapsulated" refers to an organic electroluminescent device
having a light emitting structure and a second electrode free of
surfaces that are exposed to oxygen. Depending on the composition
of the various components, the useful lifetime of the organic
electroluminescent device can be extended by encapsulation. For
example, some electrode materials and light emitting structures
deteriorate upon prolonged exposure to oxygen, moisture, or a
combination thereof. Encapsulation reduces contact of the second
electrode or the light emitting structure with oxygen or moisture.
In FIG. 3, the combination of the first electrode 210, the
non-conductive layer 240, and the conductive layer 250 can
encapsulate the second electrode 230 and the light emitting
structure 220. Various other components or structures can be added
to provide encapsulation. For example, in some embodiments,
substrates, barrier layers, edge seals, or a combination thereof
are included to further encapsulate the device.
As shown in FIG. 3 and many of the other figures included in the
application, the first electrode 210 does not extend beyond the
outer periphery of the conducting layer 250 and the non-conductive
material 240. However, in some embodiments, the first electrode is
prepared from a material that is not reactive with oxygen or
moisture. As such, the first electrode does not need to be
encapsulated and can extend beyond the part of the device that is
encapsulated.
The second electrode 230 and the light emitting structure 220 are
shown as being the same size in FIG. 3. In other embodiments, these
components do not have the same dimensions. For example, OEL device
270 shown in FIG. 4 includes a second electrode 230 having a
shorter length, width, or a combination thereof than the light
emitting structure 220. A conductive layer 250 is in electrical
communication with a surface of the second electrode 230, such as
the surface that is opposite the light emitting structure 220. The
entire area of this surface of the second electrode 210 is in
contact with a conducting layer 250. That is, there is no
non-conductive material 240 disposed on the surface of the second
electrode 230 where the opening 200 is positioned.
Another embodiment of an OEL device 280 is shown schematically in
FIG. 5. The length and width of the second electrode 230 are
similar to the corresponding dimensions of the light emitting
structure 220 and the thickness of the non-conductive material 240
is at least equal to the thickness of the light emitting structure
220. The entire area of this surface of the second electrode 230 is
in contact with a conducting layer 250. That is, there in no
non-conductive material 240 disposed on the surface of the second
electrode 230 where the opening 200 is positioned.
In FIGS. 4 and 5, the opening 200 in the non-conductive material
240 can be positioned in an area of a surface of the second
electrode 230, such as the surface that is opposite the light
emitting structure 220. The conductive layer 250 can be bonded to a
non-conductive material 240 beyond the outer periphery of the
second electrode 230. The non-conductive material 240 separates the
conductive layer from the first electrode 210, the light emitting
structure 220, or a combination thereof beyond the outer periphery
of the second electrode 230. The non-conductive material can be
bonded to other components beyond the outer periphery of the second
electrode 230.
The first and second electrodes include conducting materials such
as metals, alloys, metallic compounds, metal oxides, conductive
ceramics, conductive dispersions, and conductive polymers. Suitable
materials can contain, for example, gold, platinum, palladium,
nickel, aluminum, calcium, barium, magnesium, titanium, titanium
nitride, indium tin oxide (ITO), fluorine tin oxide (FTO),
graphite, and polyaniline. The electrodes can have a single layer
or multiple layers of conductive materials. For example, an
electrode can include a layer of aluminum and a layer of gold, a
layer of calcium and a layer of aluminum, a layer of aluminum and a
layer of lithium fluoride, or a metal layer and a conductive
organic layer. For many applications, such as display applications,
at least one of the electrodes can transmit radiation emitted by
the light emitting structure.
In some embodiments, the first electrode is an anode and the second
electrode is a cathode. The anode can be prepared from a material
having a high work function (e.g., above about 4.5 eV). Typically,
the anode can transmit radiation emitted by the light emitting
structure. Suitable materials include a thin layer of
electronegative metals such as gold, platinum, nickel, graphite,
silver, or combinations thereof. The anode can also be prepared
from a metal oxide such as, for example, indium-tin oxide.
The cathode can be prepared from a material having a low work
function (e.g., below about 4.5 eV). Suitable materials include
n-doped silicon, alkali metals, alkaline earth metals, and the
like. For example, the cathode can contain lithium, calcium,
barium, magnesium, or combinations thereof. Such cathode materials
have a tendency to react with water, oxygen, or a combination
thereof and can be advantageously protected by encapsulation.
Methods for preparing the electrodes include, but are not limited
to, sputtering, vapor deposition, laser thermal patterning, inkjet
printing, screen printing, thermal head printing, and
photolithographic patterning. The electrodes are most commonly
prepared by vapor deposition.
The light emitting structure typically contains at least one
organic electroluminescent material. The electroluminescent
material includes, but is not limited to, fluorescent or
phosphorescent material. The organic electroluminescent material
can include, for example, a small molecule (SM) emitter (e.g., a
non-polymeric emitter), a SM doped polymer, a light emitting
polymer (LEP), a doped LEP, or a blended LEP. Suitable organic
electroluminescent material is described in U.S. Pat. No. 6,358,664
and U.S. patent application Ser. Nos. 09/662,980; 09/931,598; and
10/254,237, incorporated herein by reference in their entirety. The
organic electroluminescent material can be provided alone or in
combination with any other organic or inorganic materials that are
functional or non-functional in an organic electroluminescent
display or device.
In some embodiments, the organic electroluminescent material
includes a light emitting polymer. LEP materials are typically
conjugated polymeric or oligomeric molecules that preferably have
sufficient film-forming properties for solution processing. As used
herein, "conjugated polymers or oligomeric molecules" refer to
polymers or oligomers having a delocalized .pi.-electron system
along the polymer backbone. Such polymers or oligomers are
semiconducting and can support positive and negative charge
carriers along the polymeric or oligomeric chain.
Examples of classes of suitable LEP materials include
poly(phenylenevinylenes), poly(para-phenylenes), polyfluorenes,
other LEP materials now known or later developed, and co-polymers
or blends thereof. Suitable LEPs can also be molecularly doped,
dispersed with fluorescent dyes or photoluminescent materials,
blended with active or non-active materials, dispersed with active
or non-active materials, and the like. Examples of suitable LEP
materials are described in Kraft, et al., Angew. Chem. Int. Ed.,
37, 402-428 (1998); U.S. Pat. Nos. 5,621,131; 5,708,130; 5,728,801;
5,840,217; 5,869,350; 5,900,327; 5,929,194; 6,132,641; and
6,169,163; and PCT Patent Application Publication No. 99/40655, all
of which are incorporated herein by reference.
LEP materials can be formed into a light emitting structure, for
example, by casting a solvent solution of the LEP material on a
substrate and evaporating the solvent to produce a polymeric film.
Alternatively, LEP material can be formed in situ on a substrate by
reaction of precursor species. Suitable methods of forming LEP
layers are described in U.S. Pat. No. 5,408,109, incorporated
herein by reference. Other methods of forming a light emitting
structure from LEP materials include, but are not limited to, laser
thermal patterning, inkjet printing, screen printing, thermal head
printing, photolithographic patterning, and extrusion coating. The
light emitting structure can include a single layer or multiple
layers of LEP material or other electroluminescent material.
In some embodiments, the organic electroluminescent material can
include one or more small molecule emitters. SM electroluminescent
materials include charge transporting, charge blocking, and
semiconducting organic or organometallic compounds. Typically, SM
materials can be vacuum deposited or coated from solution to form
thin layers in a device. In practice, multiple layers of SM
materials are typically used to produce efficient organic
electroluminescent devices since a given material generally does
not have both the desired charge transport and electroluminescent
properties.
SM materials are generally non-polymeric organic or organometallic
materials that can be used in OEL displays and devices as emitter
materials, charge transport materials, dopants in emitter layers
(e.g., to control the emitted color), charge transport layers, and
the like. Commonly used SM materials include
N,N'-bis(3-methylphenyl)-N,N'-diphenylbenzidine (TPD) and metal
chelate compounds such as tris(8-hydroxyquinoline) aluminum (AlQ).
Other SM materials are disclosed in, for example, C. H. Chen, et
al., Macromol. Symp. 125, 1 (1997); Japanese Laid Open Patent
Application 2000-195673; U.S. Pat. Nos. 6,030,715; 6,150,043; and
6,242,115; and PCT Patent Applications Publication Nos. WO 00/18851
(divalent lanthanide metal complexes), WO 00/70655 (cyclometallated
iridium compounds and others), and WO 98/55561, all of which are
incorporated herein by reference.
The organic electroluminescent devices can optionally include a
hole transporting layer, an electron transport layer, a hole
injection layer, an electron injection layer, a hole blocking
layer, an electron blocking layer, a buffer layer, and the like.
These and other layers and materials can be used to alter or tune
the electronic properties and characteristics of the OEL devices.
For example, such layers and materials can be used to achieve a
desired current/voltage response, a desired device efficiency, a
desired brightness, and the like. Additionally, photoluminescent
materials can be present to convert the light emitted by the
organic electroluminescent materials to another color. These
optional layers can be positioned between the two electrodes and
can be part of the light emitting structure or a separate
layer.
For example, the organic electroluminescent device can optionally
include a hole transport layer between the light emitting structure
and one of the first or second electrodes. The hole transport layer
facilitates the injection of holes into the device and the
migration of the holes towards the cathode. The hole transport
layer can further act as a barrier for the passage of electrons to
the anode. The hole transport layer can include, for example, a
diamine derivative, such as
N,N'-bis(3-methylphenyl)-N,N'-bis(phenyl)benzidine,
N,N'-bis(3-naphthalen-2-yl)-N,N-bis(phenyl)benzidine, or a
triarylamine derivative, such as
4,4',4"-tris(N,N'-diphenylamino)triphenylamine, or
4,4',4"-tris(N-3-methylphenyl-N-phenylamino)triphenylamine. Other
examples include copper phthalocyanine and
1,3,5-tris(4-diphenylaminophenyl)benzenes. Further suitable
compounds that can be included in the hole transport layer are
described in H. Fujikawa, et al., Synthetic Metal, 91, p. 161
(1997) and J. V. Gravulevicius, and P. Strohriegl, "Charge
Transporting Polymers and Molecular Glasses," Handbook of Advanced
Electronic and Photonic Materials and Devices, H. S. Nalwa (ed.),
10, pp. 233-274 (2001).
The organic electroluminescent device can optionally include an
electron transport layer between the light emitting structure and
one of the first or second electrodes. The electron transport layer
facilitates the injection of electrons and their migration towards
the recombination zone. The electron transport layer can further
act as a barrier for the passage of holes to the cathode. Suitable
materials for the electron transport layer include, for example,
tris(8-hydroxyquinolato) aluminum,
1,3-bis[5-(4-(1,1-dimethylethyl)phenyl)-1,3,4-oxadiazol-2-yl]benzene,
2-(biphenyl-4-yl)-5-(4-(1,1-dimethylethyl)phenyl)-1,3,4-oxadiazole,
and other compounds described in C. H. Chen et al., Macromol.
Symp., 125, 1 (1997) and J. V. Gravulevicius, and P. Strohriegl,
"Charge Transporting Polymers and Molecular Glasses," Handbook of
Advanced Electronic and Photonic Materials and Devices, H. S. Nalwa
(ed.), 10, pp. 233-274 (2001).
In one embodiment, the electrodes, the light emitting structure,
other optional layers, or a combination thereof can be formed by
transferring one or more layers by laser thermal patterning as
described in, for example, U.S. Pat. Nos. 6,485,884; 6,482,564;
6,284,425; 6,242,152; 6,228,555; 6,228,543; 6,221,553; 6,221,543;
6,214,520; 6,194,119; 6,114,088; 5,998,085; 5,725,989; 5,710,097;
5,695,907; and 5,693,446; in co-assigned Published U.S. Patent
Application 20020158574; and in co-assigned U.S. patent application
Ser. Nos. 09/662,980; 09/451,984; 09/931,598; and 10/004,706, all
of which are incorporated herein by reference. For example, the
organic electroluminescent material can be coated on a donor sheet
and then selectively transferred alone or in combination with other
layers or with one or more electrodes to a receptor sheet. The
receptor sheet can be pre-patterned with one or more electrodes,
transistors, capacitors, insulator ribs, spacers, color filters,
black matrix, hole transport layers, electron transport layers,
other elements suitable for electronic displays and devices, or a
combination thereof.
The organic electroluminescent devices of the invention also
include a non-conductive material that defines an opening through
which the conductive layer is in electrical communication with the
second electrode. The non-conductive material can include, but is
not limited to, ceramic material, glass material, polymeric
material, and the like.
The non-conductive material typically extends beyond the outer
periphery of the second electrode. This material can function, for
example, to separate the conductive layer from the first electrode
beyond the periphery of the second electrode. The non-conductive
layer material can be bonded to part of any of the other components
of the OEL device. The non-conductive material can also function in
conjunction with the conductive layer, the first electrode, a
substrate, or a combination thereof to encapsulate the light
emitting structure and the second electrode. Encapsulation can seal
the device and reduce migration of water or oxygen from outside the
organic electroluminescent device to the light emitting structure,
the second electrode, or a combination thereof. Encapsulation can
extend the useful lifetime of some organic electroluminescent
devices.
In some embodiments, the non-conductive material is a polymeric
material. Suitable polymeric materials include thermoplastic or
thermosetting homopolymers and thermoplastic or thermosetting
copolymers. The non-conducting polymeric material can be curable or
non-curable. Examples of non-conductive polymeric materials that
can be used include polyurethanes, polyolefins, polyacrylates,
polyesters, polyamides, epoxies, or combinations thereof. In some
embodiments, the non-conductive polymeric material is an adhesive
such as a hot melt adhesive or a pressure sensitive adhesive. The
adhesive can be tacky or non-tacky at room temperature. The acidity
of the polymeric material should not be high enough to cause
corrosion of the electrodes.
The non-conductive polymeric material can be applied as a
pre-formed layer or as a solution or dispersion. In some
embodiments, a pre-formed non-conductive layer is used such as an
adhesive layer. Examples of a suitable non-conductive layer include
ethylene vinyl acetate or modified polyolefin thermoplastics such
as 3M.TM. Thermo-bond (available from 3M of St. Paul, Minn.).
The non-conductive material can include a desiccant such as, for
example, calcium oxide. A suitable hot melt adhesive containing a
desiccant is DesiMax.TM. from Multisorb Technologies Inc. (Buffalo,
N.Y.).
An opening is made in the non-conductive layer. The opening is
positioned in an area of a surface of the second electrode, such as
in an area of the surface that is opposite the light emitting
structure. The length and width of the opening are typically about
equal to or smaller than the corresponding dimensions of the
surface of the second electrode. The conductive layer is in
electrical communication with the second electrode through the
opening in the non-conductive layer.
The pre-formed non-conductive layer preferably does not contain
particulates of a size that could lead to electrical shorting of
the device when the layer is bonded to both the conductive layer
and the first electrode beyond the outer periphery of the second
electrode. The thickness should be thick enough to prevent the
conductive layer from shorting the first and second electrodes
beyond the outer periphery of the second electrode. The thickness
should not be so thick, however, that the conductive layer cannot
be adequately deformed to provide electrical communication between
the conductive layer and the second electrode through the opening
defined in the non-conductive material. The typical thickness of
the pre-formed non-conductive layer is in the range of about 0.5
mils (0.012 mm) to about 2 mils (0.05 mm).
In some embodiments, as shown in FIG. 3, the opening 200 in the
non-conductive layer 240 is positioned over less than the entire
surface of the second electrode 230, such as the surface that is
opposite the light emitting structure 220. The non-conductive
material 240 is disposed on part of this surface of the second
electrode 230 and extends beyond the outer periphery of the second
electrode 230. In other embodiments, as shown in FIGS. 4 and 5, the
opening 200 in the non-conductive layer 240 is positioned over an
entire surface of the second electrode 230, such as the surface
that is opposite the light emitting structure 220. The
non-conductive material 240 is not disposed on any part of this
surface of the second electrode 230. That is, the entire surface
where the opening is positioned is in contact with conductive
material.
The non-conductive material can be applied as a solution or
dispersion rather than as a pre-formed film. Such material can be
applied, for example, using printing methods or masking off
regions. As shown in FIG. 3, the non-conductive material 240 can be
applied to the outer edges of a surface of the second electrode
230, such as the surface that is opposite the light emitting
structure 220. As shown in FIGS. 4 and 5, an OEL can be prepared
without any non-conductive material 240 applied to the surface of
the second electrode 230.
The non-conductive material can also be applied to part of the
other components to encapsulate the OEL device. As shown in FIGS. 3
and 5, the non-conductive material can be applied to edges of the
light emitting structure 220 and to part of a surface of the first
electrode 210. In FIG. 4, the non-conductive material 240 is
applied to part of one surface of the light emitting structure 220,
the edges of the light emitting structure 220, and part of a
surface of the first electrode 210.
The same types of conductive materials that can be used in the form
of a pre-formed layer can be used in the form of a dispersion or
solution. The compositions preferably do not contain compounds that
are reactive with other materials in the device and contain a
minimum of species that can migrate through the various layers of
the device.
The conductive layer includes materials such as metals, metallic
alloys, metallic compounds such as metal oxides, conductive
ceramics, and conductive polymers. In some embodiments, the
conductive layer can include a metal or metallic compound
containing gold, silver, copper, indium tin oxide, aluminum, and
the like.
The conductive layer can be a deformable film. Suitable deformable
films include metals such as copper, silver, gold, aluminum, or the
like. The conductive layer typically has a thickness in the range
of about 1 to about 2 mils (about 0.025 to about 0.05 mm). The
surface roughness of the conductive layer is preferably less than
the thickness of the cathode (e.g., about 100 to 300 nm). The
conductive layer is preferably free of defects such as pinholes
that would allow introduction of moisture or oxygen into the
organic electroluminescent device.
The conductive layer can contact a surface of the second electrode
directly or be separated from the second electrode by another
conductive material such as, for example, a conductive polymeric
adhesive. By providing a conductive layer having low resistivity in
electrical communication with the second electrode, the resulting
organic electroluminescent device can advantageously have
substantial illumination over a large area without significant loss
of illumination intensity across the device.
In some embodiments, an entire surface of the second electrode,
such as the surface opposite the light emitting structure, is in
direct contact with the conductive layer. In other embodiments, all
but the outer portion of a surface of the second electrode, such as
the surface opposite the light emitting structure, is in direct
contact with the conductive layer through a single opening in the
non-conductive material. In still other embodiments, a surface of
the second electrode, such as the surface opposite the light
emitting structure, is in direct contact with the conducting layer
through multiple openings in the non-conductive material.
The openings can have any desired shape. The shape can be regular
or irregular. When multiple opening are present, the shape of the
openings can be uniform or non-uniform. The multiple openings can
be arranged in any desired configuration that is ordered or random.
For example, FIG. 13 shows a schematic cross-sectional view of an
embodiment in which the organic electroluminescent device 380
includes a plurality of openings 200 in the non-conductive material
240 through which contact can be made between the conductive layer
250 and the second electrode 230. The multiple openings can be
arranged in a linear arrangement.
The organic electroluminescent device can further include a
substrate. For example, as shown schematically in FIG. 6A for
device 290, the first electrode 210 can be disposed on a substrate
300. The first electrode 210 is positioned between the substrate
300 and the light emitting structure 220. The substrate 300 is
typically transparent. As used herein, "transparent" refers to a
material that transmits at least some of the light emitted by the
electroluminescent material in the light emitting structure. The
substrate can be flexible or rigid.
Suitable rigid transparent substrates include, for example, glass,
polycarbonate, acrylic, and the like. Suitable flexible transparent
substrates include for example, polyesters (e.g., polyethylene
terephthalate, polyester naphthalate, and polycarbonate),
polyolefins (e.g., linear, branched, and cyclic polyolefins),
polyvinyls (e.g., polyvinyl chloride, polyvinylidene chloride,
polyvinyl acetals, polystyrene, polyacrylates, and the like),
cellulose ester bases (e.g., cellulose triacetate, cellulose
acetate), polysulphones such as polyethersulphone, and other
conventional polymeric films.
The substrate, the conductive layer, or both can be notched to
enhance flexibility of the device. The notches can be in one
direction or multiple directions across the substrate, conductive
layer, or both. The notches can have a variety of shapes such as
slits, V-shaped, or U-shaped. The notches typically extend to less
than about 50 percent of the thickness of the substrate or the
conductive layer. FIG. 14a is a schematic cross-sectional view of
one embodiment of an organic electroluminescent device having
V-shaped notches across the substrate. FIG. 14b is a schematic
cross-sectional view of one embodiment of an organic
electroluminescent device having V-shaped notches across the
conductive layer.
The organic electroluminescent device can include two substrates as
shown in FIG. 6B for device 490. The first electrode 210 is
disposed on a first substrate 300. Substrate 300 can be laminated
to a second conductive layer 410 disposed on a second substrate
440. The first electrode 210 is in electrical contact with the
second conductive layer 410 through electrical interconnect 420 and
electrical interconnect attachment layer 430. The light emitting
structure 220 is disposed on the first electrode 210. The second
electrode 230 is disposed on the light emitting structure 220. A
first conductive layer 250 is in electrical communication with the
second electrode 230 through an opening 200 defined in the
non-conductive material 240. The electrical interconnect 420 and
the electrical interconnect attachment layer 430 are electrically
insulated from the second electrode 230 and the first conductive
layer 250 by the non-conductive material 240.
In this embodiment, the first electrode, second electrode, and
light emitting structure can be formed on the first substrate 300.
This assembly can then be attached to the second conductive layer
410 and the second substrate to provide further protection for the
reactive components in the device.
In FIG. 6B, the electroluminescent structure that includes the
first electrode 210, the light emitting structure 220, and the
second electrode 230 is encapsulated on one side by the first
substrate 300, the second conductive layer 410, and the second
substrate 440. The electroluminescent structure is encapsulated on
the opposite side by the non-conductive layer 240 and the first
conductive layer 250. The anode contact is the second conductive
layer 410 and the cathode contact is the first conductive layer
250. The device 490 can be hermetically sealed without having to
pattern the device anode.
In some embodiments, the electrical interconnect 420 and electrical
interconnect attachment layer 430 is a single layer such as solder.
In other embodiments, the electrical interconnect layer 420 is a
metal foil, a metal wire, or a metallized plastic and the
electrical interconnect attachment layer 430 is a conductive
adhesive or solder. The electrical interconnect layer 420 and the
electrical interconnect attachment layer 430 both conduct
electricity.
Suitable materials for the second conductive layer 410 are
typically transparent and includes a thin layer of electronegative
metals such as gold, platinum, nickel, graphite, silver, or
combinations thereof. This layer can also be prepared from a metal
oxide such as, for example, indium-tin oxide. In some embodiments,
the second conductive layer is patterned.
The second substrate 440 can be prepared from the same materials as
the first substrate 300. For example, the second substrate can be
prepared from glass, polycarbonate, acrylic, polyesters (e.g.,
polyethylene terephthalate, polyester naphthalate, and
polycarbonate), polyolefins (e.g., linear, branched, and cyclic
polyolefins), polyvinyls (e.g., polyvinyl chloride, polyvinylidene
chloride, polyvinyl acetals, polystyrene, polyacrylates, and the
like), cellulose ester bases (e.g., cellulose triacetate, cellulose
acetate), polysulphones such as polyethersulphone, and other
conventional polymeric films. The second substrate can include a
barrier construction, examples of which are described later.
FIG. 6C is a schematic cross-sectional view of an organic
electroluminescent device 480 having a substrate and edge seals 400
to further encapsulate the second electrode 230 and light emitting
structure 220. The edge seals 400 can be prepared from a plastic
material such as a polyolefin or epoxy. A desiccant material such
as calcium oxide can be include in the composition used to prepare
the edge seals.
As shown in FIG. 6C for device 480 with edge seals 400 and in FIG.
6D for device 510 without edge seals, the first electrode 210 can
extend beyond the outer periphery of the non-conductive material
240 and the conductive layer 250. Such a device can be prepared
using a material for the first electrode 210 that is not reactive
with oxygen or moisture. Suitable materials for the first electrode
include, for example, gold, platinum, nickel, graphite, silver, or
combinations thereof. This electrode can also be prepared from a
metal oxide such as, for example, indium-tin oxide. The
non-conductive material 240 can be bonded to both the conductive
layer 250 and the first electrode beyond the periphery of the
second electrode.
FIG. 7 shows a schematic cross-sectional view of another embodiment
of an organic electroluminescent device 310 that includes a
substrate. The non-conductive polymeric material 240 and a
conductive layer 250 are laminated to the substrate 300 rather than
to the first electrode as shown in FIGS. 3, 4, 5, and 6a-d. In this
embodiment, the first electrode 210, second electrode 230, and
light emitting structure 220 are encapsulated by the combination of
the substrate 300, the conductive layer 250, and the non-conductive
material 240. This embodiment can be used advantageously when the
first electrode 210 is constructed of a material that can react
with moisture or oxygen.
When both of the electrodes are reactive with oxygen or moisture,
the first electrode 210 can be in electrical communication with a
non-reactive conductive material that extends beyond the device.
For example, vias can pass through the substrate and the vias can
contain a non-reactive conductive material.
FIG. 8 shows a schematic cross-sectional view of yet another
embodiment of an organic electroluminescent device 340 that
includes a substrate 300. The first electrode 210 can be disposed
in a well. The well can be formed, for example, by removal of part
of the substrate, such as by etching. Alternatively, the well can
be formed by printing an electrode and a non-conductive material on
the surface of the substrate in the form of, for example, parallel
stripes or a grid.
The substrate can include any number of devices or components
suitable in OEL devices or displays. Suitable devices or components
include, for example, transistor arrays and other electronic
devices; color filters, polarizers, wave plates, diffusers, and
other optical devices; insulators, barrier ribs, black matrix, mask
work and other such components; and the like.
The substrate can include a barrier construction. As used herein,
the term "barrier construction" refers to a structure that reduces
the migration of moisture, oxygen, or a combination thereof across
the substrate to contact the light emitting structure and the
electrodes of the organic electroluminescent device. The barrier
construction is typically transparent and can include one or more
layers. Exemplary barrier constructions can contain a plurality of
layer pairs (i.e., dyads) that include a barrier material layer and
polymeric smoothing material layer supported on a substrate. In
some embodiments, the lifetime of the organic electroluminescent
device can be extended by the use of a barrier construction.
The barrier construction can include a metal containing layer. The
metal containing layer typically includes a metal oxide, metal
nitride, metal carbide, metal oxynitride, or a combination thereof.
Suitable materials for the metal containing layer include, for
example, silicon oxide, aluminum oxide, titanium oxide, indium
oxide, tin oxide, zirconium oxide, indium tin oxide, aluminum
nitride, silicon nitride, boron nitride, silicon carbide, and
aluminum oxynitride, silicon oxynitride, and boron oxynitride. In
some embodiments, the metal containing layer includes a metal oxide
such as aluminum oxide or indium tin oxide. Suitable materials are
described in U.S. Pat. Nos. 6,231,939 and 5,725,909 and PCT Patent
Applications Publication No. WO 00/26973, all of which are
incorporated herein by reference in their entirety.
The metal containing layer of the barrier construction is typically
less than about 300 nm thick. The barrier construction can also
include at least one polymeric layer in addition to the metal
containing layer. For example, the barrier construction can be
prepared by laminating alternating layers of polymeric layers and
metal containing layers.
FIG. 9 shows a schematic cross-sectional view of an OEL device 350
that includes a substrate 300 having a metal containing layer 330
and a polymeric layer 320. The polymeric layer 320 of the barrier
construction typically contains polyacrylates, polyesters,
polyolefins, or combinations thereof. In FIG. 9, the metal
containing layer 330 of the barrier construction is between the
first electrode 210 and the polymeric layer 320. In other
embodiments the polymeric layer 320 is adjacent to the first
electrode 210. The polymeric layer can function to preserve the
integrity of the thin metal containing layer. Minor cracks or
defects in the metal containing layer can increase the migration of
moisture and oxygen across the barrier construction into contact
with the second electrode, the light emitting structure, or a
combination thereof. A plurality of layer pairs of polymeric and
metal containing layers typically increases the resistance to
migration of moisture and oxygen.
An electroluminescent device of the invention can include a
plurality of first electrodes, a plurality of organic
electroluminescent materials, a plurality of second electrodes, or
a combination thereof. FIG. 10A shows a schematic cross-sectional
view of an embodiment in which the organic electroluminescent
device 360 includes a plurality of second electrodes 230. FIG. 10B
shows a schematic top view of the same device. The plurality of
second electrodes 230 can be arranged linearly or in any
configuration over the first electrode 210 and the light emitting
structure 220.
The organic electroluminescent device 360 shown in FIG. 10A and
FIG. 10B can be prepared by disposing a light emitting structure
220 on a first electrode 210. Multiple second electrodes 230 can be
disposed on the surface of the light emitting structure 220
opposite the first electrode 210. Multiple opening 200 can be
defined in a non-conductive material 240. The openings 200 can be
positioned entirely within an area of a surface of the second
electrode, such as the surface opposite the light emitting
structure. The non-conductive material 240 is disposed between each
of the second electrodes 230 and covers the surfaces of the light
emitting structure 220 not in contact with the first electrode 210
or the second electrode 230. A conductive layer 250 is in
electrical communication with each of the second electrodes 230
through the openings 200 defined in the nonconductive material 240.
The conductive layer 250 can be separated from the light emitting
structure 220 and the first electrode 210 by the non-conducting
material 240 beyond the periphery of the second electrode 230.
In the device 360 shown in FIGS. 10A and 10B, the plurality of
second electrodes 230 can be addressed simultaneously because a
single conductive layer 250 is in electrical communication with all
the second electrodes. Such a device can be illuminated over a
large area without a significant loss of the illumination intensity
across the device.
In contrast to device 360 in FIGS. 10A and 10B, a device containing
a plurality of first electrodes or a device containing a plurality
of first electrodes and a plurality of second electrodes can be
addressed in multiple locations. That is, such a device can be used
to form a device or display having multiple pixels. FIGS. 11A, 11B,
12A, and 12B are schematic cross-sectional views of an organic
electroluminescent devices that contain a plurality of first
electrodes 210. FIGS. 11A, 12A, and 12B include a plurality of
first electrodes 210 and second electrodes 230.
FIG. 11A is a schematic cross-sectional view of device 370
containing a plurality of first electrodes 210, a non-patterned
light emitting structure 220, and a plurality of second electrodes
230. FIG. 11B is a schematic cross-sectional view of device 450
containing a plurality of first electrodes 210, a non-patterned
light emitting structure 220, and a non-patterned second electrode
230. The first electrode in these devices can be prepared, for
example, by disposing a plurality of first electrodes 210 and a
plurality of non-conductive materials in a pattern such as parallel
stripes or a grid on a substrate 300. Any two dimensional pattern
can be used to print the first electrodes 210 on the substrate
300.
In some embodiments, the organic electroluminescent device can be a
multiple color display. For example, the OEL device 390 shown in
FIG. 12A and OEL device 500 shown in FIG. 12B can contain a
plurality of organic electroluminescent materials patterned between
a plurality of first electrodes 210 and a plurality of second
electrodes 230. The different organic electroluminescent materials
can emit light of different wavelengths. A non-conductive material
460 can separate the plurality of first electrodes and second
electrodes from each other. The non-conductive material 460 can be
the same material as 240 or can be different. The non-conductive
material 460 can be, for example, a black matrix.
Another aspect of the invention provides methods for preparing
organic electroluminescent devices. In one embodiment, an
electroluminescent structure is formed that includes, but is not
limited to, a first electrode, a second electrode, a light emitting
structure, a conductive layer, and a non-conductive material. The
light emitting structure is disposed between the first and second
electrodes. An opening in the non-conductive material is formed and
positioned in an area of a surface of the second electrode, such as
the surface opposite the light emitting structure. The area of the
opening in the non-conductive material is typically about equal to
or smaller than the area of the surface of the second electrode
over which the opening is positioned. Electrical communication can
be established between the conductive layer and the second
electrode through the opening in the non-conductive material.
The method can involve encapsulating the second electrode and the
light emitting structure. For example, the conductive layer and the
non-conductive material can extend beyond the periphery of the
second electrode. The non-conductive material can separate the
conductive layer from other active components of the OEL device
beyond the periphery of the second electrode. A seal can be formed
by using the non-conductive material to laminate the conductive
layer to the first electrode, the substrate or both beyond the
periphery of the second electrode.
As an example, organic electroluminescent devices of the invention
can be prepared by depositing a conductive material to form a first
electrode that is transparent to the radiation of interest (e.g.,
the radiation emitted by the light emitting structure). One or more
layers of organic electroluminescent materials can be disposed on
the first electrode to form a light emitting structure. A second
electrode can be disposed on light emitting structure such that the
light emitting structure is between the first and second
electrodes.
One or more openings can be formed in a non-conductive material
such as, for example, an adhesive layer having a release liner on
one surface or both surfaces. The opening can be cut through the
adhesive layer and at least one of the release liners by, for
example, die cutting, kiss cutting, or other methods. One release
liner can then be removed and the adhesive attached to either the
conductive layer or second electrode(s). The second release liner
can then be removed and the conductive layer can be coupled to the
second electrode(s) and the remainder of the structure via the
adhesive layer.
The openings can be positioned in an area of a surface of the
second electrode, such as the surface opposite the light emitting
structure. Upon removal of the release liner, the adhesive layer
can be bonded to a conducting layer such that the conducting layer
is in electrical communication with the second electrode through
the opening in the adhesive layer.
The method can be a roll-to-roll process. The electroluminescent
structure can be constructed on a first roll. For example, the
first electrode can be deposited on a roll of substrate or can be
available without a substrate on a roll. The light emitting
structure and the second electrode can be disposed on a surface of
the first electrode such that the light emitting structure is
positioned between the two electrodes. The non-conductive material
and the conducting layer can be provided in the form of a second
roll and third roll, respectively. At least one openings can be
formed in the second roll. The second roll can be laminated between
the first and third rolls such that the opening is aligned with a
surface of the second electrode and electrical communication is
established between the conductive layer and the second electrode
through the opening in the non-conductive layer.
The adhesive layer and the conductive layer can both extend beyond
the outer periphery of the second electrode. The adhesive layer can
function to laminate the conductive layer to the first electrode or
the substrate beyond the outer periphery of the second electrode,
thereby encapsulating the organic electroluminescent device. The
adhesive layer also functions to separate the conducting layer from
other active components of the OEL device such as the first
electrode beyond the outer periphery of the second electrode. The
adhesive layer can also function to seal the device.
The lamination temperature can be sufficient to soften or melt the
adhesive layer. In some embodiments, the temperature is typically
kept below about 100.degree. C. For example, the lamination
temperature can be kept below about 60.degree. C. to reduce the
likelihood of damage to the device layers such as the light
emitting structure.
The organic electroluminescent devices can be an active or passive
display or device. A passive display or device typically has the
anode and cathode oriented at 90 degree angles from each other,
although other orientations are possible.
The organic electroluminescent devices of the invention can be
used, for example, for general lighting purposes or as backlights.
Constructions of the backlights can include bare or circuitized
substrates, anodes, cathodes, hole transport layers, electron
transport layers, hole injection layers, electron injection layers,
emissive layers, color changing layers, and other layers and other
materials suitable for organic electroluminescent devices.
Constructions can also include polarizers, diffusers, light guides,
lenses, light control films, brightness enhancement films, and the
like. Applications include white and single color large area single
pixel lamps and multiple colored large area single pixel lamps.
The organic electroluminescent devices of the invention can be used
as low resolution displays. Constructions can include bare or
circuitized substrates, anodes, cathodes, hole transport layers,
electron transport layers, hole injection layers, electron
injection layers, emissive layers, color changing layers, and other
layers and materials suitable in OEL devices. Constructions can
also include polarizers, diffusers, light guides, lenses, light
control films, brightness enhancement films, and the like.
Applications include graphic indicator lamps (e.g., icons);
segmented alphanumeric displays (e.g., appliance time indicators);
small monochrome passive or active matrix displays; small
monochrome passive or active matrix displays plus graphic indicator
lamps as part of an integrated display (e.g., cell phone displays);
large area pixel display tiles (e.g., a plurality of modules, or
tiles, each having a relatively small number of pixels), such as
may be suitable for outdoor display used; and security display
applications.
The organic electroluminescent devices of the invention can be used
as high resolution displays. Constructions can include bare or
circuitized substrates, anodes, cathodes, hole transport layers,
electron transport layers, hole injection layers, electron
injection layers, emissive layers, color changing layers, and other
layers and materials suitable in OEL devices. Constructions can
also include polarizers, diffusers, light guides, lenses, light
control films, brightness enhancement films, and the like.
Applications include active or passive matrix multicolor or full
color displays; active or passive matrix multicolor or full color
displays plus segmented or graphic indicator lamps (e.g., laser
induced transfer of high resolution devices plus thermal hot stamp
of icons on the same substrate); and security display
applications.
The foregoing describes the invention in terms of embodiments
foreseen by the inventor for which an enabling description was
available, notwithstanding that insubstantial modifications of the
invention, not presently foreseen, may nonetheless represent
equivalents thereto.
EXAMPLES
Example 1
Covion PDY132 light emitting polymer (LEP) was used to make a
flexible organic light emitting diode (OLED) with a circular
emitting area of one inch in diameter.
A UV-curable polymer solution was made containing 80 grams of
Ebecryl.TM. 629 (UCB Chemicals, Smyrna, Ga.), 20 grams of SR399
(Sartomer Company, Exton, Pa.) and 2 grams of Irgacure.TM. 184
(Ciba Specialty Chemicals, Tarrytown, N.Y.) dissolved in 1000 grams
of Methyl Ethyl Ketone. The resulting solution was coated on a 100
micron PET film (HSPE 100 available from Teijin Corp., Japan) using
a Yasui Seiki model CAG150 coater fitted with a 110R knurl at a web
speed of 20 ft/min. The coating was dried in-line at 70.degree. C.
and cured with an F-600 Fusion D UV lamp operating at 100% power.
The resulting polymer coated web was then sequentially coated with
35 nm of ITO, 10 nm of Ag and 35 nm of ITO to obtain a sheet
resistance of 15 ohms/square. The ITO/Ag/ITO coating remained
unpatterned.
A small piece of the ITO/Ag/ITO coated PET was cut from the roll to
be used for device fabrication. The piece was cleaned in an
ultrasonic cleaning system. The ITO surface was then plasma treated
for 2 minutes at a base pressure of 0.030 torr, oxygen flow rate of
500 sccm and Rf power of 400 watts, in a Plasma Science plasma
treater (Model PS 500 available from AST Inc. of Billerica,
Mass.).
PEDOT 8000 (poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate)
also known as PEDT/PSS, available from H. C. Starck, Leverkusen,
Germany) was diluted with IPA and spin coated onto the ITO surface
using a vacuum spin coating chuck. Spinning at 3000 rpm for 30
seconds resulted in a PEDOT 8000 thickness of 90-100 nm. The PEDOT
was dried in a 65.degree. C. nitrogen purge oven for 10 minutes.
The pieces were transferred into a nitrogen atmosphere glove box
and are placed onto a 100.degree. C. hot plate for 2 minutes for
further PEDOT 8000 drying. The PEDOT 8000 was a conductive polymer
and functioned as a buffer layer.
Covion PDY132 LEP (0.5 wt % in toluene, available from Covion
Organic Semiconductors GmbH, Frankfurt, Germany) was spin coated
onto the PEDOT 8000 surface using a vacuum chuck. Spinning at 2500
rpm for 30 seconds resulted in a 75 nm film.
A small portion of the ITO surface was cleaned of LEP and PEDOT for
contacting the ITO as the anode. A 50.times.50 mm square was cut
from the piece.
Calcium was then deposited 400 .ANG. thick via thermal evaporation
onto the LEP surface through a mask with a one inch diameter
opening. Silver was then vacuum deposited to 3000 .ANG. thick on
top of the calcium using the same method and mask.
The encapsulation materials were prepared by cutting a 0.5 inch
diameter hole out of the middle of a 35 mm.times.35 mm piece of
3M.TM. Thermo-bond 845. The 3M.TM. Thermo-bond was laminated at
300.degree. F. (148.degree. C.) to a 35 mm.times.35 mm piece of 4
mil (0.1 mm) copper foil. The piece of 3M.TM. Thermo-bond/copper
was placed on top of a 300.degree. F. (148.degree. C.) hotplate
with the copper facing down and 3M.TM. Thermo-bond facing up with
the liner removed. The 3M.TM. Thermo-bond /copper was allowed to
reach temperature for 5-10 minutes.
The flexible OLED device was placed in contact with, and allowed to
stick to, the 3M.TM. Thermo-bond; the construction was then removed
from the hot plate, placed on the floor of the glove box and the
two pieces were laminated together with a hand roller. The
resulting encapsulated OLED device emitted light when the copper
foil and ITO coating were connected to the leads of a battery.
Example 2
Several orange-red emitting OLED devices were prepared on 22 mm
square (1.0 mm thick) ITO coated glass (15 ohm/square, Colorado
Concept Coatings LLC, Longmont, Colo.). The ITO coating was not
patterned and thus covered the entire surface of the glass
substrate. The ITO coated substrates were cleaned by rubbing with a
methanol soaked lint-free cloth (Vectra Alpha 10, Texwipe Co., LLC,
Upper Saddle River, N.J.) followed by a 4 minute oxygen plasma
treatment (full power and 5 psi oxygen, Plasma-Preen II-973,
Plasmatic Systems, Inc., North Brunswick, N.J.).
An aqueous solution of
(poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (1%
solids, Baytron P 4083, Bayer, Leverkuesen, Germany) was spin
coated onto the cleaned, etched substrates to give a 50 nm film.
The Baytron P 4083 was a conductive polymer and functioned as a
buffer layer. The Baytron P 4083 and ITO coated substrates were
dried for 15 minutes on a 110.degree. C. hot plate under a flow of
nitrogen.
The coated substrates were transferred to a bell jar evaporation
chamber and evacuated to about 10.sup.-6 torr. Layers of 300 .ANG.
thick N,N'-bis(3-naphthalen-2-yl)-N,N'-bis(phenyl)benzidine (NPD,
from H. W. Sands Corp., Jupiter, Fla.); 300 .ANG. thick
9,10-bis(2-naphthyl)anthracene (ADN from Eastman Kodak Co.,
Rochester, N.Y.) doped with 1%
4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-
pyran (DCJTB, from Eastman Kodak Co., Rochester, N.Y.); and 200
.ANG. thick tris(8-hydroxyquinolinolato)aluminum (AlQ, from H. W.
Sands Corp., Jupiter, Fla.) were thermally deposited in sequence
through a shadow mask containing a 19.5 mm square opening. The NPD
functioned as a hole transport layer, the ADN and AlQ functioned as
an electron transport layers, and DCJTB was a fluorescent dye used
as a dopant to alter the color of the light emission.
The organic coated substrates were transferred to glove box that
contained a thin film evaporation chamber (Edwards 500, BOC
Edwards, England) for the thermal deposition of cathodes. Layers of
100 .ANG. thick AlQ (from H. W. Sands Corp., Jupiter, Fla.), 7
.ANG. thick LiF (from Alfa-Aesar Co., Ward Hill, Mass.), 200 .ANG.
thick Al (from Alfa-Aesar Co., Ward Hill, Mass.), and 1,000 .ANG.
thick Ag (from Alfa-Aesar Co., Ward Hill, Mass.) were sequentially
deposited at about 10.sup.-7 torr onto the organic coated
substrates through a metal shadow mask that contained a 1 cm.sup.2
circular opening disposed such that the cathode was in the
approximate center of the substrate.
A piece of 3M.TM. Thermo-Bond 845-EG thermal laminating film on
release liner (2.5 mil adhesive thickness) approximately
100.times.50 mm was cut from a roll of the material. The release
liner was marked to form a 2.times.8 grid of 25 mm squares. A 6 mm
circular hole was cut in the center of each 25 mm square using a
hand-held pliers-type paper punch. This was placed onto an
approximately 125.times.75 mm piece of 0.05 mm thick Al foil
(McMaster-Carr Supply Co., Chicago, Ill.) with the adhesive side
contacting the foil. This assembly was in turn placed on an
aluminum plate (3.times.9.times.0.025 inches, The Q-panel Company,
Cleveland, Ohio) with the release liner side contacting the
aluminum plate. This was then feed three times in succession
through a 2-roll thermal laminator (TDE Systems model HL-406, Kmart
Corp., Troy, Mich.) operating at approximately 102.degree. C. to
laminate the adhesive film to the Al foil and deform the foil into
the 6 mm hole in the adhesive.
The laminated Al foil was removed from the aluminum carrier plate,
cut with scissors into 25 mm squares, and brought into the glove
box containing the orange-red emitting OLED devices. One of the 25
mm squares was trimmed with scissors to about 16 mm square such
that the 6 mm hole in the adhesive layer remained at the
approximate center of the film. The release liner was then removed
and the encapsulating film was placed onto the cathode side of one
of the 22 mm square OLED devices such that the adhesive layer of
the encapsulation film was in contact with the OLED device and the
6 mm hole through the adhesive layer was approximately centered
over the cathode of the device. The cathode and its peripheral area
were completely covered by the encapsulating film. The
encapsulating film was thermally laminated to the OLED device in
the inert nitrogen atmosphere of the glove box by passing the
assembly through a 2 roll thermal laminator (Bestech model 2962,
Rose Art Industries, Livingston, N.J.) that operated at about
100.degree. C.
Upon cooling, anode connections to the encapsulated OLED were made
by contacting the ITO of the substrate anywhere on the periphery of
the Al encapsulating film and cathode connections were made by
contacting any portion of the Al encapsulation film. When current
was applied, orange-red light was emitted from the device. At 6
mA/cm.sup.2 the current-voltage-luminance characteristics of the
laminated device were essentially unchanged from the device
characteristics prior to the thermal lamination encapsulation
procedure.
* * * * *